JPH0823054B2 - Ti / Ti5 Si3 System Functionally Gradient Material and Manufacturing Method Thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

This invention relates to Ti / Ti ₅ Si ₃
The present invention relates to a functionally graded functional material and a method for manufacturing the same. More specifically, the present invention is a new Ti which is useful for structural materials for aerospace, engines, turbines, chemical devices, etc., is lightweight, can be used in harsh environments, and is capable of forming complex shapes. / Ti ₅ Si ₃ -based functionally graded material and a method for producing the same.

[0002]

2. Description of the Related Art Materials having a homogeneous composition, such as metals and alloys, have made great progress through research and development so far and are widely used in various fields. However, there is an increasing interest in materials having excellent functions that cannot be realized by such homogeneous materials, and from now on, research and development of materials that are non-homogeneous and have advanced functions will proceed. is expected. The development of such high-performance non-homogeneous materials is also the key to the progress of advanced technology. For example, in high-speed flying vehicles, the outer wall is exposed to high temperatures, but the inner wall must be at a temperature at which humans can live. A laminated composite material of ceramics and metal, which has characteristics of heat resistance and high strength, is considered to be applied to such an application. However, in practice, such composite materials cannot be used. This is because the coefficient of thermal expansion of metal differs from that of ceramics by one digit, the contact surface separates due to thermal expansion, and ceramics is brittle, making it difficult to manufacture a reliable large member. Therefore, with the aim of breaking this bottleneck, a graded composition material or a graded functional material in which the mixing ratio of ceramics and metals is continuously changed has been proposed.

As a method for producing this functionally graded material, there has been known a method of successively stacking raw materials in which the mixing ratio of metal and ceramics is changed by a vapor phase growth method, a thermal spraying method, a powder metallurgy method or the like. It is also used in practice. However, this method has the drawback that the deposition rate of the material is slow, the process is complicated, and the productivity is poor. Therefore, it is difficult to manufacture a member having a large size or a complicated shape, and the product becomes abnormally expensive. Therefore, although its characteristics and expectations for its application are great, the functionally graded material has not yet been established as a composition, a structure of a structure, and a manufacturing method that are significant for practical use, so that it still has an industrial perspective. Is not cultivated.

The present invention has been made in view of the above circumstances, and an object of the present invention is to overcome the technical limitations of conventional functionally graded materials, and to provide a new material structure and a manufacturing method therefor. There is.

[0005]

In order to solve the above problems, the present invention provides Ti or its alloy region, T
It has an i ₅ Si ₃ -based compound region and a mixed region of Ti or its alloy and Ti ₅ Si ₃ -based compound. In this mixed region, the ratio of Ti or its alloy phase and Ti ₅ Si ₃ phase is almost continuous. A Ti / Ti ₅ Si ₃ having a graded composition characterized in that a Ti-rich portion of the mixed region that has changed and is in contact with the Ti region and a Ti ₅ Si ₃ -rich portion is in contact with the Ti ₅ Si ₃ region Provide a functionally graded material.

Further, the present invention is a method in which Ti ₅ Si ₃ compound is laminated on Ti or its alloy, or Ti ₅ S
Ti / Ti ₅ having a graded composition characterized by heating to a temperature of 1600 K or higher after coating with an i ₃ -based compound
A method for manufacturing a Si ₃ -based functionally graded material is also provided.

[0007]

In other words, the present invention proposes a combination of materials for producing a functionally graded material which is high in performance and easy to manufacture and a technique for making the functionally graded material. The functionally graded material here is composed of a Ti ₅ Si ₃ intermetallic compound region having a high melting point and excellent lightness and oxidation resistance, Ti or an alloy region thereof, and a mixed region of both existing between them, and a mixed region. In, the distribution density of both substances changes continuously. In the present invention, the functionally graded material is manufactured from Ti or its alloy molded material and the Ti ₅ Si ₃ based compound only by the heat treatment utilizing the phase relationship and the structure control technique.

Since the thermal expansion coefficient of the Ti ₅ Si ₃ based intermetallic compound is much closer to that of metal than that of ceramics, the thermal strain caused by the difference in thermal expansion coefficient is much smaller than that of conventional functionally graded materials. For this reason, cracks caused by a steep temperature gradient and thermal fatigue are significantly reduced as compared with conventional functionally graded materials. The intermetallic compound Ti ₅ Si ₃ has a low specific gravity of 4.3, a high melting point of 2400K, and excellent oxidation resistance, and is the most suitable intermetallic compound as a material facing a harsh environment. There is. Further, the reaction temperature used for producing the functionally graded material is as high as 1600K, which is unprecedented in other material systems. This means that the manufactured functionally gradient material can be used at a sufficiently high temperature.

The functionally graded materials proposed so far have poor manufacturability, but the present invention solves this problem all at once. This is because in the present invention, a Ti / Ti ₅ Si ₃ -based functionally gradient material is realized by utilizing eutectic bonding. In the present invention, Ti is pure titanium or T
It means various titanium alloys such as i-Al and Ti-Al-V type, and the Ti ₅ Si ₃ type compound is an intermetallic compound Ti ₅ Si.
₃ as a base, which was added to the composition controls the other elements within the solid solubility limit of Ti ₅ Si ₃ phase and the set beyond the solid solubility limit
Ti ₅ S containing small amounts of other crystal structures and metals by adjusting the composition
i ₃ group alloy, also further contain unavoidable impurities component
Means of.

This eutectic bonding is carried out as a heat treatment at a temperature of 1600 K or higher.
Alternatively, it is necessary to bring the alloy and the Ti ₅ Si ₃ based compound into close contact. As a method for adhering the Ti ₅ Si ₃ compound to the Ti alloy, various forms can be considered depending on the shape of Ti or its alloy member. For example, not only lamination by simple superposition but also coating by thermal spraying, physical
For example, vapor deposition by a chemical method and powder spraying. In the present invention, all of these operations for adhering Ti or its alloy and Ti ₅ Si ₃ based compound for the purpose of eutectic bonding are allowed.

Explaining the eutectic bonding further, first, FIG. 1 shows a binary equilibrium diagram of Ti--Si. From this figure, Ti and Ti ₅ Si ₃ coexist in an equilibrium state. It can be seen that a eutectic reaction exists at about 1600 K between the two. This is because when the temperature is raised to 1600 K or higher, the interface between Ti and Ti ₅ Si ₃ begins to melt and a melt having a eutectic composition (E in FIG. 1) is formed. This increase in the melt amount is determined by the rate of dissolution of Ti from the solid phase Ti into the melt and the rate of dissolution of the solid phase Ti ₅ Si ₃ into the melt.

The temperature of the Ti and Si ₅ Si ₃ bond pair was set to 170
When the temperature is raised to 0K, the composition between 1a and 1b in FIG. 1 becomes a melt. The amount of the melt increases as Ti or Ti ₅ Si ₃ dissolves in the melt, but this melt causes the melt near the solid phase interface on the Ti side to have composition a and the solid phase on the Ti ₅ Si ₃ side to melt. The melt at the position close to the interface is kept in the composition b. Then, the composition of the melt between both ends continuously changes. That is, the formation of a graded composition in the melt. On the other hand, part of the melt penetrates into the Ti-side and Ti ₅ Si _3- side solid phases through grain boundaries and the like.

[0013] For behavior during cooling of the gradient composition melt formed, Ti in the melt of the Ti side than composition E, but also the Ti ₅ Si ₃ is a Ti ₅ Si ₃ side the melt from the E nucleus Generate-Grow. The remaining melt decreases in amount as it cools and approaches the composition of E. In the melt having the composition E, at 1600 K, Ti and Ti ₅ Si ₃ crystallize simultaneously to form a so-called eutectic structure. That is, the structure formed after cooling becomes Ti primary crystal, eutectic crystal, and Ti ₅ Si ₃ primary crystal corresponding to the graded composition. This texture distribution shows that the gradient composition is realized by heating to a temperature of 1600K or higher.

As a result of such eutectic reaction, Ti / Ti ₅
The Si ₃ -based eutectic solidification structure is a layered structure in which Ti and Ti ₅ Si ₃ are alternately stacked. However, since the granular structure is generally superior to the layered structure in terms of ductility and toughness, the granular structure is more resistant to cracking due to thermal shock or thermal gradient. Therefore, Ti /
It is also effective to modify the Ti ₅ Si ₃ eutectic structure.

When the joint is homogenized and reheated at a temperature of 1600 K or less, the layered structure produced by the eutectic reaction is granulated, and the ductility and toughness of the material are improved. Hereinafter, the present invention will be described in more detail with reference to Examples.

[0016]

EXAMPLE 10 × 10 from a Ti ₅ Si ₃ button ingot melted in a non-consumable electrode type argon arc melting furnace
× collected specimens of 5 mm, this superimposing a Ti plate of the same size, Ti-Ti ₅ S in an argon gas atmosphere
After heating at 1633 K, which is higher than the i ₃ eutectic temperature, for 3.6 ks to melt-diffusion bond Ti and Ti ₅ Si ₃ , the furnace was cooled. At this time, no peeling or cracking was observed at the interface between the base material and the bonding layer.

In the structure of the bonding layer thus produced, granular Ti ₅ Si ₃ first appears in αTi on the Ti base metal side, and then α
It changed into a layered structure of Ti and Ti ₅ Si ₃ in Ti, and then to an overall layered structure. Ti ₅ Si ₃ T when approaching the base metal side
i ₅ Si ₃ layer tissue during, followed by granular αTi in Ti ₅ Si _3, finally had become Ti ₅ Si ₃ matrix. Then, in this way subjected to 86.4ks annealing at 1573K in Ti / Ti ₅ Si ₃ based bonding material formed by the lamellar structure of the bonding layer disappears, particulate is Ti base metal Ti ₅ Si
_The texture containing ₃ and granular αT on the Ti ₅ Si ₃ base metal side
The organization changed to include i. FIG. 2 shows a sectional SEM image in this state.

[0018]

According to the present invention as described above, the following excellent effects can be obtained. 1) A functionally gradient material having a complicated shape can be easily manufactured. That is, although the concept of functionally graded material has existed up to now, it has been far away from the object of practical use due to the complexity of the manufacturing process.
According to the present invention, it can be easily manufactured and put into practical use.

2) The Ti / Ti ₅ Si ₃ system functionally graded material is lightweight and can be used in a harsh environment. For this reason, it can be used as a body material for space transit machines and SST. It can be applied to aircraft and automobile engines, turbines for power generation, etc. to achieve high performance. 3) Ti / Ti ₅ Si ₃ -based functionally gradient material is an easily repairable material that can be used in a harsh environment.

Therefore, for example, an energy-related device such as coal liquefaction operates in a harsh environment, and it is a bottleneck that there is no material capable of withstanding it, which hinders equipment development. It is expected that this will make significant progress in the future.

[Brief description of drawings]

FIG. 1 is a binary system equilibrium diagram of Ti—Si.

FIG. 2 is a cross-sectional microscope (SEM) photograph as a drawing substitute for a Ti / Ti ₅ Si ₃ functionally gradient material as an example.

Claims (4)

[Claims] 1. Ti or its alloy region, Ti ₅ Si
₃ type compound area and Ti or its alloy and Ti ₅ S
There is a mixed region of the i ₃ -based compound. In this mixed region, the ratio of Ti or its alloy phase and the Ti ₅ Si ₃ phase changes almost continuously, and the Ti-rich portion in the mixed region is T
The part that is in contact with the i region and is enriched with Ti ₅ Si ₃ is Ti ₅ S
T having a graded composition characterized by being in contact with the i ₃ region
i / Ti ₅ Si ₃ system functionally graded material. 2. The gradient according to claim 1, wherein Ti or a Ti ₅ Si ₃ -based compound is laminated on Ti or an alloy thereof, or Ti ₅ Si ₃ -based compound is coated and then heated to a temperature of 1600 K or higher. Ti / Ti ₅ Si ₃ with composition
Of manufacturing functionally graded functional materials. 3. The method according to claim 2, wherein the heating is performed in vacuum or in an inert gas. 4. Ti / Ti ₅ Si ₃ for reheating the material obtained according to claim 2 or 3 below 1600 K.
Of manufacturing functionally graded functional materials.